The invention relates to a front projection screen for visibly displaying an image in an audience space, which image is supplied by an image beam from a primary image source, said screen comprising a plate having a front side facing the audience space and the image source, said plate having a Fresnel structure for converging the image beam in the audience space and having means for spreading light of the image beam in the audience space.
A front projection screen of this type is known from FR-A No. 2,413,685. The front side of the front projection screen described in this Patent Application has a Fresnel structure and an anisotropic layer in which the incident light is reflected and spread in a diffuse manner. The function of the Fresnel structure is to converge the image beam from the image source to the viewers in the audience space. The image observed in the audience space therefore has a comparable brightness throughout the screen. The anisotropic layer spreads the light so that the projected image is visible in the whole audience space. This is accomplished by providing the layer proximate to the front side of the screen so that the spreading of light in one direction is larger than in the transverse direction.
A problem with images projected on projection screens is that the contrast of the observed image is reduced due to ambient light incident on the screen and subsequently being reflected towards the audience. In the case of a diffusely reflecting projection screen, such as the known screen, substantially all the incident ambient light is reflected. In addition, the anisotropic reflecting layer in the known screen requires special materials and manufacturing techniques to obtain the anisotropy, with the same extent of diffusion in the entire plate.